The physical layer is responsible for electromagnetic compatibility including electromagnetic spectrum frequency allocation and specification of signal strength, analog bandwidth, etc. It provides a standardized interface to the transmission medium, including a mechanical specification of electrical connectors and cables, for example maximum cable length, an electrical specification of transmission line signal level and impedance. The physical layer performs bit-by-bit or symbol-by-symbol data delivery over a physical transmission medium. The major functions and services performed by the physical layer are: It does not define a layer that deals exclusively with hardware-level specifications and interfaces, as this model does not concern itself directly with physical interfaces. The Internet protocol suite, as defined in RFC 1122 and RFC 1123, is a high-level networking description used for the Internet and similar networks. performs symbol encoding, transmission, reception and decoding and,.
Within the semantics of the OSI model, the physical layer translates logical communications requests from the data link layer into hardware-specific operations to cause transmission or reception of electronic (or other) signals. It is a fundamental layer underlying the higher level functions in a network, and can be implemented through a great number of different hardware technologies with widely varying characteristics. The physical layer consists of the electronic circuit transmission technologies of a network. 3 Relation to the Internet protocol suite.
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